[volt-nuts] LTZ1000 resistors, lower collector currents

[David C. Partridge]

me.uk ist gleich als z.b. mich.de 


Dave
-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On Behalf Of Frank Stellmach
Sent: 07 November 2011 20:06
To: volt-nuts at febo.com
Subject: [volt-nuts] LTZ1000 resistors, lower collector currents

John,

all drift parameters of R1, R4, R5 were attenuated by the circuitry by a factor of 100, R2 and R3 by a factor of 300. Therefore, bulk metal foil is not needed, also wirewound precision resistors will do.

Their T.C. is between < 1 - 3ppm/K, compared to (+/-1 +/-2) ppm/K of the S, K types, which is exactly the same.
Even the Z202 type Vishay resistors are no better than (0.2 +/-2) ppm/K.

Therefore, the contribution to T.C. for all types is about 0.02.. 
0.03ppm/K or less. I think, that's to be neglected, as 0.1ppm/K total is very fine.

Drift over time of ww. vs. molded metal foil is exactly the same, i.e. 
20ppm/yr shelf life, contributing 0.2ppm/yr. max., compared to the 1..2ppm/ yr. typical for the LTZ @ 45°C.

I have built my two LTZ references on wirewound resistors, afters 3 years of nearly continous powering, I have not seen a drift bewteen both, against a Fluke 5442A, and a third LTZ in my 3458A in the last 1,5 years of more than 1..2 ppm. Temperature drift effects I also could not distinguish from other stationary/reversible drifts.

If you are living in UK (what is: 'me.uk'?) , visit rhopointcomponents.co.uk.

They have those 0.1% wirewound resistors 'econistor 8E16/8G16' on stock, I have used for the LTZ

They sell also those very stable metal foil resistors "FLCY" from japanese manufacturer alpha electronics (swallowed recently by Vishay), which I have used for my Hammond type reference divider, which is also ultra stable after years.

Its a little bit more difficult to find FLCY values for R2/R3, but 25K/2K should do the job...


Frank

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